ESEN
Management area
Contact
Tools

Reverse DNS / PTR

Resolve the PTR of any IPv4/IPv6 and check forward-confirmation (FCrDNS). In your browser via DoH.

Queries go to Cloudflare and Google public DoH resolvers. Nothing passes through our servers.

About this tool

Reverse DNS resolves the PTR record of any IPv4 or IPv6 and checks forward confirmation (FCrDNS), that is, that the name the IP points to resolves back to that same IP. All from your browser via DoH.

  • Get the hostname (PTR) associated with an IP address.
  • Validate FCrDNS, a common requirement for mail servers.
  • Diagnose why a sending server is rejected or flagged as spam.

Frequently asked questions

Why does PTR matter for email?

Many servers reject mail from IPs without a PTR or with a generic PTR. A correct reverse DNS that matches the HELO greatly improves the reputation and deliverability of a sending server.

What is FCrDNS?

Forward-Confirmed reverse DNS: the IP has a PTR to a name, and that name resolves back to the same IP. It is a consistency check used by antispam and reputation services.